Boiler detention trough



Patented Sept. 21, 1948 BGHTER. DETENTION TEOUGH .lames F. Spaht, `Baton Rouge, La.,4 assignor` pment Company, a cor- Standard Oil Devolo poration of Delaware Application December 7, 1944, Serial No. 567,107

i claims. (c1. zio- 414i This invention relates to the treatment of boiler feed water containing scale-forming compounds, and in` particular relates to the removal of the scalefforming constituents by reaction with sodium phosphatel compounds under improved treating conditions.

It is well known that scale-forming compounds scale forms upon the inner surface of a boiler,

considerable loss of heat transfer occurs and difficulties also occur with priming and corrosion of the equipment.

The usual treatment to remove the scale-forming constituents from water is effected either within the boiler itself or, as more generally applied, partly before introducing into the boiler and partly in the boiler itself. 'Ihe treatment of Water prior to entering the boiler is usually made by the lime soda or base exchange processes, The secondary chemical treatment in the boiler is usually made to obviate the formation of an adherent `scale. upon the innersurface. In this latter treatment, the precipitates, formed are removed as suspended materials in the `water by a blowing down process. The present invention is an improvement in the means for treating boiler water involving the main treatment in the -boiler itself.

When the scale-forming constituents are reacted withsuch reactive phosphates as the alkali metal ortho-phosphates, and particularly trisodium phosphate, the calcium and magnesium compounds so formed are sometimes gelatinous in character and are diicult to remove by the normal blow down contacted the boiler heating surface. The invention involves the chemical treatment of water containing hardescale--forming constituents by the reaction of these compounds with a reactive alkali metal phosphate such as trisodium phosphate formed in the treating system. It is a feature of the invention that the reactive phosphate is produced by the reaction in situ of an alkali metal phosphate with a mixture of natural boiler procedure, once having 2 feed water` and some boiler water containing sufcient alkali to react with the alkali metal phosphate to `form tri-alkali metal phosphate. The reaction by which scale-forming constituents are precipitated also` occurs according `to the inven-` tion in 'a special portion of the boiler system termed a detention trough. The detention trough is of such` a design as to allow mixing of the boiler feed water, made alkaline with a quantity of high alkaline boiler water, and the alkali metal phosphates. By virtue of the alkalinity present, all` phosphates are converted to tri-alkali metal phosphates, which react with the hardness constituents to produce a precipitate, The precipitate is removed from the detention trough by .blowing down from that point.

yl'n `order that the invention may be more fully understood, illustration is presented of sections l through a typical boiler system containing a pre- Lil) erred form of `a detention trough according to the invention. Thus, Figure l is a cross-sectional view of a boiler systemand Figure 2 is a longitudinal section showing further details of the detention trough. t l l In Figure 1 the -boiler has a reference numeral l0. Within the `boiler is the detention trough l2. Within the` detention trough i2 is located the chemical solution supply line i4 and the boiler feed water line i6. Outside the opening of the boiler feed line I6 is the supply ofthe boiler water intothe` detention trough. The two pipes it and i8 areso located as to` furnish a mixing Zone near the end of the pipe 43x inside the detention trough I2. Atthe base of the detention trough l2 is the sludge removal line 2t. At the other end of the detention trough is the openinglzQ into the boiler through which `the treated water passes into the boiler lil, The boiler l0 has at its lower portion a `continuous blow-down line 2.4.

t In Figure 2, the various features are shown in longitudinal cross sections. In addition also, showing islpresented .of the distribution plates 25 to assist in `the reaction between the alkali water and the alkali metal phosphate introduced f' through line I4.

The following data are presented as illustrative of the processing according to the invention. In this case, samples were obtained from a Babcock and Wilcox, Integral, rZOO-pound boiler. Approximately l5 pounds of monosodium phosphate 3 per million pounds of feed water were being added to the boiler feed water Within the detention trough.

phosphate suflicient to react With substantially all the scale forming constituents in the natural water, entirely within said treatment zone, fand The effect of pI-I on the reaction of the monosodium phosphate with the alkaline boiler w-ater is indicated by a comparison of samples A and C. Sample A from the detention trough contained parts per million monosodium phosphate and 2.5 parts per million trisodium phosphate. On admixture of more basic boiler water and Water from the detention trough, and after heating at 200 F. for one hour, hardness constituents were completely removed; 2.5 parts per million of monosodium phosphate and 25 parts per million of trisodium phosphate were detected. On standing for 30 minutes, sample D showed a drop in the turbidity of the mixture from 30 to 15 parts per million. This is indicative of the degree of settling obtainable in the detention trough of the invention.

The treating procedure of the invention furnishes boiler feed water from which steam without conveyant solid particles may be produced. It has been found that Water treated in accordance with the present invention is advantageous for all boiler pressures encountered in power plant operation. These advantageous features of the process are considered primarily due to the increased facility for settling of the precipitate formed after the reaction in the trough due to its depth. It hasalso been found that the treatment is especially advantageous when, due to a particular series of circumstances, natural waters must be used for boiler feed supply means. 1t has also been found advantageous where jet condensers are installed and under such conditions Where it is necessary that boilers, in order to operate at high capacities, produce clean v steam that is free of scale and sludge.

The invention having now been described and illustrated with regard to a preferred embodiment, it is desired that it be understood that, although specic terms have been employed, such terms are used generically and in a descriptive sense and not for the purpose of limitation.

What is claimed is:

l. A process for removing scale forming constituents from natural water, comprising supplying an aqueous solution of an alkali metal phosphate to a confined treatment Zone within a boiler, and subject to heat therefrom, supplying natural feed Water to said Zone in admixture with a qluantity of water from said boiler, said Iboiler Water containing alkaline constituents in sufficient quantity to form in situ with said alkali metal phosphate a tri-alkali metal continuously removing reaction products from the lower portion of said Zone While discharging the treated water from the upper portion thereof.

2. A process according to claim 1 in which the alkali metal phosphate is a mono-alkali metal phosphate.

3. A process according to claim 1 in 'which the alkali metal phosphate is sodium dihydrogen phosphate.

4; Apparatus for the treatment of natural water Vto substantially remove scale for-ming constituents therefrom, comprising a boiler `con-- taining a quantity of heated alkaline water, a. detention trough in said boiler, partially sub-y merged in the boiler water and heated thereby; means for supplying a natural feed Water to said trough, means for supplying an aqueous solution of an alkali metal phosphate to said trough, means for adding water from said boiler to the contents of said trough which comprises an eductor communicating with the boiler and discharging into said detention trough including a nozzle through which the natural 'Water is discharged so as to draw boiler Water from the boiler into the detention trough, means for dis charging reaction products from the lower por-y tion of said trough, and means for discharging treated water from the upper portion ofthe trough into the boiler above the water level therein.

JAMES F. SPAHT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain Feb. 8, 1934 

